The Uptake of 6‐Methoxy‐1,2,3,4‐Tetrahydro‐β‐carboline and its Effect on 5‐Hydroxytryptamine Uptake and Release in Blood Platelets

Abstract

The uptake of 6‐methoxy‐1,2,3,4‐tetrahydro‐β‐carboline (6‐MeOTHBC, 5‐methoxytryptoline) by rabbit blood platelets was studied by using ³H‐labelled compound. A high rate active uptake (Km 6.6 μM), which was inhibited by 5‐hydroxytryptamine (5‐HT) and cinnanserine, and a slow rate uptake, not inhibited by 5‐HT were observed. The intracellular distribution of ³H‐6‐McOTHBC in platelets clearly differed from that of ¹⁴C‐5‐HT. 6‐MeOTHBC also competitively inhibited the high‐rate active (but not the slow passive) uptake of ¹⁴C‐5‐HT, being more active than 5‐HT itself. The spontaneous release of the newly taken‐up ¹⁴C‐5‐HT from platelets was increased only with high concentrations of 6‐MeOTHBC.